On Wed, Sep 12, 2012 at 3:13 PM, Dave Airlie <airlied@xxxxxxxxx> wrote: > On Wed, Sep 12, 2012 at 8:58 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: >> On Wednesday, September 12, 2012, Dave Airlie wrote: >>> On Wed, Sep 12, 2012 at 7:32 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >>> > On Tue, 11 Sep 2012, Rafael J. Wysocki wrote: >>> > >>> >> Hi, >>> >> >>> >> On Tuesday, September 11, 2012, Dave Airlie wrote: >>> >> > Hi Rafael, >>> >> > >>> >> > I've been investigating runtime PM support for some use-cases on GPUs. >>> >> > >>> >> > In some laptops we have a secondary GPU (optimus) that can be powered >>> >> > up for certain 3D tasks and then turned off when finished with. Now I >>> >> > did an initial pass on supporting it without using the kernel runtime >>> >> > PM stuff, but Alan said I should take a look so here I am. >>> >> >>> >> Alan Stern or Alan Cox? :-) >>> >> >>> >> > While I've started to get a handle on things, we have a bit of an >>> >> > extra that I'm not sure we cater for. >>> >> > >>> >> > Currently we get called from the PCI layer which after we are finished >>> >> > with our runtime suspend callback, will go put the device into the >>> >> > correct state etc, however on these optimus/powerxpress laptops we >>> >> > have a separate ACPI or platform driver controlled power switch that >>> >> > we need to call once the PCI layer is finished the job. This switch >>> >> > effectively turns the power to the card completely off leaving it >>> >> > drawing no power. >>> >> > >>> >> > No we can't hit the switch from the driver callback as the PCI layer >>> >> > will get lost, so I'm wondering how you'd envisage we could plug this >>> >> > in. >>> >> >>> >> Hmm. In principle we might modify pci_pm_runtime_suspend() so that it >>> >> doesn't call pci_finish_runtime_suspend() if pci_dev->state_saved is >>> >> set. That would actually make it work in analogy with pci_pm_suspend_noirq(), >>> >> so perhaps it's not even too dangerous. >>> > >>> > This sounds more like a job for a power domain. Unless the power >>> > switch is already in the device hierarchy as a parent to the PCI >>> > device. >>> >>> I'll have to investigate power domains then, >>> >>> The switch is hidden in many different places, one some laptops its in >>> a ACPI _DSM on one GPU, on others its in an ACPI _DSM on the other >>> one, in some its in a different ACPI _DSM, then we have it in the ACPI >>> ATPX method on others, and finally Apple have it in a piece of hw that >>> isn't just on the LPC bus or somewhere like that. >>> >>> Currently we just hide it all inside vga_switcheroo and I'd just need >>> an interface to call that once the layers have stopped poking >>> registers in PCI config space, if we could fix PCI runtime suspend so >>> the driver was the last to g 2et called then that would also not suck. >> >> Well, as I said, we may try to change the PCI layer so that it doesn't >> access the device any more in pci_pm_runtime_suspend() if it sees that >> pci_dev->state_saved has been set by the driver's callback. Then, >> your drivers would only need to set pci_dev->state_saved in their >> .runtime_suspend() callbacks. >> > > Actually it appears I'll need this, I'd forgotten things are a bit > messier than I thought > > So there are two variants on the _DSM for nvidia dual-gpu machines, > the older pre-optimus _DSM requires > an explicit power off call post-D3, however for optimus _DSM the D3 > transition will flick the power switch, however > the pci code then goes and seem to turn the device back to D0 for some > reason. So yes after save state, > I'd really appreciate if it the pci layer would stop poking my device. > >> Alternatively, which may be less hackish but more work, you can set the >> pm_domain pointer in the device structure to a struct dev_pm_domain whose >> ops will just call the corresponding bus type's ops except for >> .runtime_suspend() that will execute the additional ACPI stuff after calling >> the bus type's method. > > I've mostly written this, and it seems to work, I've jsut set a > pm_domain in the vga switcheroo code that copies the dev->bus->pm > into a private structure. I'll need this for the old nvidia and radeon > poweroffs. > http://cgit.freedesktop.org/~airlied/linux/log/?h=drm-opt-pwr is my current WIP branch http://cgit.freedesktop.org/~airlied/linux/diff/drivers/gpu/vga/vga_switcheroo.c?h=drm-opt-pwr&id=8952007a8799a5b096d64a8217e3001e2ebed2ab contains what I've done to override the 2 pms ops we need to override for older GPUs http://cgit.freedesktop.org/~airlied/linux/commit/?h=drm-opt-pwr&id=005fdf5c184f9b857cbd8cb7195898d776f68670 is my current PCI workaround. Dave. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
